In this work, we theoretically investigate optical bistability and optical response of a hybrid system consisting of semiconductor quantum dot (SQD) coupled with a vanadium dioxide nanoparticle (VO2NP) in the infrared (IR) regime. The VO2 material exists in semiconductor and metallic phases below and above the critical temperature, respectively where the particle optical properties dramatically change during this phase transition. In our calculations a filling fraction factor controls the VO2NP phase transition when the hybrid system interacts with a laser field. We demonstrate that the switch-up threshold for optical bistability is strongly controlled by filling fraction without changing the structure of the hybrid system. Also, it is shown that, the threshold of optical bistability increases when the VO2NP phases changes from semiconductor to metallic phase. The presented results have the potential to be applied in designing optical switching and optical storage.
We numerically investigate the electromagnetically induced transparency (EIT) of a hybrid system consisting of a three-level quantum dot (QD) in the vicinity of vanadium dioxide nanoparticle (VO2NP). VO2NP has semiconductor and metallic phases where the transition between the two phases occurs around a critical temperature. When the QD-VO2NP hybrid system interacts with continuous wave laser fields in an infrared regime, it supports a coherent coupling of exciton–polariton and exciton–plasmon polariton in semiconductor and metal phases of VO2NP, respectively. In our calculations a filling fraction factor controls the VO2NP phase transition. A probe and control laser field configuration is studied for the hybrid system to measure the absorption of QD through the filling fraction factor manipulations. We show that for the VO2NP semiconductor phase and proper geometrical configuration, the absorption spectrum profile of the QD represents an EIT with two peaks and a clear minimum. These two peaks merge to one through the VO2NP phase transition to metal. We also show that the absorption spectrum profile is modified by different orientations of the laser fields with the axis of the QD-VO2NP hybrid system. The innovation in comparison to other research in the field is that robust variation in the absorption profile through EIT is due to the phase transition in VO2NP without any structural change in the QD-VO2NP hybrid system. Our results can be employed to design nanothermal sensors, optical nanoswitches, and energy transfer devices.
We propose an optimized quasiperiodic microcavity with the aim of achieving the highest quality factor. The proposed structure consists of two quasicrystal rings with different geometries. By performing several optimizations on the structure, the highest quality factor of 8.16×107 for a femtosecond laser with a wavelength of 1040 nm can be achieved. The quasiperiodic microcavity is used for a quantum dot laser application that obtained the highest output power of 3800 W/m2. The most important characteristics of this structure are the improvement of the quality factor and a simultaneously stable cavity wavelength.
The thermally induced stress in pulsed pump solid state lasers with super-Gaussian profile has been investigated. An
analytical expression for the thermal stress is introduced. We consider the heat deposited in the crystal due to the pump.
The temperature distribution in the crystal has been calculated by solving the non-steady state heat conduction equation.
A Ti: Sapphire crystal is assumed pumped by a pulse laser. All the stress components have been obtained and discussed
in details. The results show that the non-homogenous temperature distribution is induced by the thermal stress in the
The effect of thermal lensing is a critical factor for resonator design and must be considered to improve the beam quality.
The absorption of the pump radiation by laser material and surface cooling leads to a nonuniform temperature
distribution in the rod. In this letter the temperature distribution in a cylindrical Nd:YAG rod under repetitive flash lamp
pulses is numerically simulated, when pumped by flash lamp with 150 μs pulse width and 10 Hz repetition rate . We
consider Gaussian pump pulse shape in time and redial absorption in laser rod. Our calculations show that the
temperature converges to a finite value and doses evolve in time noticeably. Also by computing the changes of refraction
index, we obtain the focal length of the heat dispersion.